FINAL TECHNICAL REPORT

September 1, 1995, through August 31, 1996

Project Title: USE OF FBC ASH AND SO2 CONTROL BY-PRODUCTS FOR LINERS AND ALKALI SUBSTITUTES

ICCI Project Number: 95-1/3.2A-5

Principal Investigator: Dr. B. C. Paul, Southern Illinois University at Carbondale

Other Investigators: Dr. S. Esling, Southern Illinois University at Carbondale

Project Manager: Dr. Dan Banerjee, ICCI

ABSTRACT

In this project SO2 control byproducts were used to construct full commercial scale liners and infiltration barriers at two sites. Liners are used by municipal and special waste landfills to prevent water from contacting materials that might release contaminants into the environment. These liners have traditionally been built of clay and/or geomembranes. Wet sulfite scrubber byproduct can be packed to clay like permeabilities and FBC ashes can be added to regular soils to produce permeabilities lower than most clays. It was the objective of this study to conduct a full scale pilot project to show that SO2 control byproducts are economical and effective as alternatives to traditional liner materials. Both projects demonstrated that the SO2 control byproducts could be easily handled by conventional earth moving equipment at prices as low or lower than the use of traditional clays. A video showing the construction techniques used was produced as an extra benefit of this years project. Monitoring of the sites has to date indicated that the liners built are highly effective as infiltration barriers and do not loose their integrity at least in the first year. Networks of environmental monitoring stations and equipment have found no contamination of ground or surface waters as a result of using these materials and the direct leachate and run-off of FBC ash has been shown to contain only high levels of sodium and potassium, but no unusual toxic trace elements. The sites are to be monitored for two more years with a final report to ICCI on long term behavior and impacts.

As a result of successful pilot projects, one of Illinois's three scrubbed power stations now ships 100% of its scrubber byproduct for recycling as cap and liner material. The power plant has dismantled its on site landfilling capability since it is no longer needed. Plans for rail facilities to haul between 1/4th and 1/2 of Illinois's FBC ashes for liner applications are being made, though final agreement and construction is still pending. One issue is the fugitive dust from FBC ash handling in the field. A dust containment device is being built with ICCI sponsorship next year to address the dust problem.

EXECUTIVE SUMMARY

In this project SO2 control byproducts were used to construct full commercial scale liners and infiltration barriers at two sites. Liners are used by municipal and special waste landfills to prevent water from contacting materials that might release contaminants into the environment. These liners have traditionally been built of clay and/or geomembranes. Wet sulfite scrubber byproduct can be packed to clay like permeabilities and FBC ashes can be added to regular soils to produce permeabilities lower than most clays. It was the objective of this study to conduct a full scale pilot project to show that SO2 control byproducts are economical and effective as alternatives to traditional liner materials and that when used in this way pose no threat to the environment.

To accomplish this objective, two tasks were spelled out for this years project.

Task #1 Monitor the FBC ash cap at Thunderbird.

Task #2 Instrument and monitor a sulfite scrubber byproduct cap at Harco.

To fulfill task #1, five types of monitoring were specified.

1- Monitor rainfall to determine the amount of water available to infiltrate through the cap.

2- Monitor groundwater wells to discern direction of flow and to determine if contaminants were entering the groundwater as a result of the 10,000 tons of FBC ash used in the 7 acre cap.

3- Monitor a series of elevation monuments placed to determine if the expansive cementitious reactions common for FBC ash were causing heaving that might threaten liner integrity.

4- Monitor lysimeters placed beneath the cap last year to determine if water was seeping through the cap and how much.

5- Monitor sampling stations along Briar Creek to determine if contaminants from the cap were being carried into the creek by surface run-off.

Although final answers to some of the questions implied by this type of monitoring require the two additional year monitoring study funded by ICCI, at the end of this years project the investigators are pleased to announce that these tasks have been completed, that the liner has been completely effective in blocking vertical infiltration, that there are no signs of heave to threaten liner integrity, and there are no indications of contamination to surface or groundwater resources.

Task #2 specified installation and operation of the following types of monitoring devices

1- A rain gage.

2- Four free draining lysimeters to detect infiltration through the cap and to investigate the purity of any water that does infiltrate.

3- Six time domain reflectometer probes and six tensiometers to measure water front position in the vadose zone beneath the cap and to distinguish between lateral and vertical water infiltration.

4- Six suction lysimeters to cross check water front positions and measure the quality of pore water that may be in too small a quantity to flow without an external driving force.

5- Ring infiltrometers to test the response of instrumentation to induced infiltration and to possibly measure the permeability of the cap in the field.

6- Groundwater monitoring wells to determine impacts on groundwater quality.

The above equipment was to be installed in two instrument stations. The construction work, which was not funded by ICCI or under the direct control of the researchers, was delayed by internal reorganization at the Department of Natural Resources. The cap has now been built and the two instrument stations installed. Some devices for the stations will not be delivered till September 10 and will be installed at that time. The monitoring wells must be installed after the changes in groundwater flow due to construction have been established. As the parts and agreements for the well installations have been made, there will be no cost or problem going forward with next years monitoring project.

The projects at both Harco and Thunderbird demonstrated that the SO2 control byproducts could be easily handled by conventional earth moving equipment at prices as low or lower than the use of traditional clays. A video showing the construction techniques used was produced as an extra benefit of this years project. Monitoring of the sites has to date indicated that the liners built are highly effective as infiltration barriers and do not loose their integrity at least in the first year. Networks of environmental monitoring stations and equipment have found no contamination of ground or surface waters as a result of using these materials and the direct leachate and run-off of FBC ash has been shown to contain only high levels of sodium and potassium, but no unusual toxic trace elements. The sites are to be monitored for two more years with a final report to ICCI on long-term behavior and impacts.